From: Dave Hansen <haveblue@us.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk,
hch@infradead.org, Dave Hansen <haveblue@us.ibm.com>
Subject: [PATCH 01/23] rearrange may_open() to be r/o friendly
Date: Wed, 11 Jul 2007 17:17:11 -0700 [thread overview]
Message-ID: <20070712001711.ED55C482@kernel> (raw)
In-Reply-To: <20070712001710.654CD9ED@kernel>
may_open() calls vfs_permission() before it does checks for
IS_RDONLY(inode). It checks _again_ inside of vfs_permission().
The check inside of vfs_permission() is going away eventually.
With the mnt_want/drop_write() functions, all of the r/o
checks (except for this one) are consistently done before
calling permission(). Because of this, I'd like to use
permission() to hold a debugging check to make sure that
the mnt_want/drop_write() calls are actually being made.
So, to do this:
1. remove the IS_RDONLY() check from permission()
2. enforce that you must mnt_want_write() before
even calling permission()
3. enable a debugging in permission()
We need to rearrange may_open(). Here's the patch.
---
lxc-dave/fs/namei.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff -puN fs/namei.c~rearrange-permission-and-ro-checks-in-may_open fs/namei.c
--- lxc/fs/namei.c~rearrange-permission-and-ro-checks-in-may_open 2007-07-10 12:46:01.000000000 -0700
+++ lxc-dave/fs/namei.c 2007-07-10 12:46:01.000000000 -0700
@@ -228,6 +228,10 @@ int permission(struct inode *inode, int
{
umode_t mode = inode->i_mode;
int retval, submask;
+ struct vfsmount *mnt = NULL;
+
+ if (nd)
+ mnt = nd->mnt;
if (mask & MAY_WRITE) {
@@ -252,7 +256,7 @@ int permission(struct inode *inode, int
* the fs is mounted with the "noexec" flag.
*/
if ((mask & MAY_EXEC) && S_ISREG(mode) && (!(mode & S_IXUGO) ||
- (nd && nd->mnt && (nd->mnt->mnt_flags & MNT_NOEXEC))))
+ (mnt && (mnt->mnt_flags & MNT_NOEXEC))))
return -EACCES;
/* Ordinary permission routines do not understand MAY_APPEND. */
@@ -1546,10 +1550,6 @@ int may_open(struct nameidata *nd, int a
if (S_ISDIR(inode->i_mode) && (flag & FMODE_WRITE))
return -EISDIR;
- error = vfs_permission(nd, acc_mode);
- if (error)
- return error;
-
/*
* FIFO's, sockets and device files are special: they don't
* actually live on the filesystem itself, and as such you
@@ -1564,6 +1564,10 @@ int may_open(struct nameidata *nd, int a
flag &= ~O_TRUNC;
} else if (IS_RDONLY(inode) && (flag & FMODE_WRITE))
return -EROFS;
+
+ error = vfs_permission(nd, acc_mode);
+ if (error)
+ return error;
/*
* An append-only file must be opened in append mode for writing.
*/
_
next prev parent reply other threads:[~2007-07-12 0:17 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-07-12 0:17 [PATCH 00/23] Mount writer count API (read-only bind mounts prep) Dave Hansen
2007-07-12 0:17 ` Dave Hansen [this message]
2007-07-12 0:17 ` [PATCH 02/23] create cleanup helper svc_msnfs() Dave Hansen
2007-07-12 0:17 ` [PATCH 03/23] filesystem helpers for custom 'struct file's Dave Hansen
2007-07-12 0:17 ` [PATCH 04/23] r/o bind mounts: stub functions Dave Hansen
2007-07-12 0:17 ` [PATCH 05/23] elevate write count open()'d files Dave Hansen
2007-07-12 0:17 ` [PATCH 06/23] r/o bind mounts: elevate write count for some ioctls Dave Hansen
2007-07-12 0:17 ` [PATCH 07/23] elevate writer count for chown and friends Dave Hansen
2007-07-12 0:17 ` [PATCH 08/23] make access() use mnt check Dave Hansen
2007-07-12 0:17 ` [PATCH 09/23] elevate mnt writers for callers of vfs_mkdir() Dave Hansen
2007-07-12 0:17 ` [PATCH 10/23] elevate write count during entire ncp_ioctl() Dave Hansen
2007-07-12 0:17 ` [PATCH 11/23] elevate write count for link and symlink calls Dave Hansen
2007-07-12 0:17 ` [PATCH 12/23] elevate mount count for extended attributes Dave Hansen
2007-07-12 0:17 ` [PATCH 13/23] elevate write count for file_update_time() Dave Hansen
2007-07-12 0:17 ` [PATCH 14/23] mount_is_safe(): add comment Dave Hansen
2007-07-12 0:17 ` [PATCH 15/23] unix_find_other() elevate write count for touch_atime() Dave Hansen
2007-07-12 0:17 ` [PATCH 16/23] elevate write count over calls to vfs_rename() Dave Hansen
2007-07-12 0:17 ` [PATCH 17/23] nfs: check mnt instead of superblock directly Dave Hansen
2007-07-12 0:17 ` [PATCH 18/23] elevate writer count for do_sys_truncate() Dave Hansen
2007-07-12 0:17 ` [PATCH 19/23] elevate write count for do_utimes() Dave Hansen
2007-07-12 0:17 ` [PATCH 20/23] elevate write count for do_sys_utime() and touch_atime() Dave Hansen
2007-07-12 0:17 ` [PATCH 21/23] sys_mknodat(): elevate write count for vfs_mknod/create() Dave Hansen
2007-07-12 0:17 ` [PATCH 22/23] elevate mnt writers for vfs_unlink() callers Dave Hansen
2007-07-12 0:17 ` [PATCH 23/23] do_rmdir(): elevate write count Dave Hansen
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